Comparison of Vs30 and F0 Values by the Single Station Earthquake-to-Microtremor Ratio (EMR) Method to Those by Traditional Multi-Station Array-Based Site Characterization Methods
Session: Data Fusion and Uncertainty Quantification in Near-Surface Site Characterization [Poster]
Type: Poster
Date: 4/30/2020
Time: 08:00 AM
Room: Ballroom
Description:
Standard in-situ methods for site characterization, including invasive downhole and non-invasive surface multi-station arrays, can be expensive and sometimes impractical for estimating the time-averaged shear-wave velocity (VS) of the upper 30 m (VS30) and the site fundamental frequency (f0), which are typically used as inputs for ground motion models to account for site effects. We explore the feasibility of using data directly recorded with a single seismic station and the inversion method of Nagashima et al. (2014) on horizontal-to-vertical spectral ratios (HVR). Input is either the earthquake HVR (EHVR) or pseudo EHVR (pEHVR) converted from microtremors using the earthquake-to-microtremor ratio (EMR) method (Kawase et al., 2018). We also test microtremor HVR (MHVR) as a direct substitute for EHVR. Using EHVR, pEHVR and MHVR, we compute VS profiles for each parameter at 31 stations in southern California assessed by Yong et al. (2019) and compare the resultant VS30 and f0 values to previous estimates based on in-situ methods. We apply the same analyses for an additional 28 sites with varying site conditions (196 m/s < VS30 < 760 m/s) in the Anza-Imperial Valley region of southern California (Fletcher and Boatwright, 2020). Our preliminary analyses of stations PFO (VS30 = 760 m/s) and DRE (VS30 = 196 m/s) show it may be necessary to develop an EMR correction factor specific for southern California—which is consistent with findings by Ito et al. (2018) for the Grenoble Basin in France. We continue with analyses and discuss our findings on the relations of VS30 and f0 to EHVR, pEHVR and MHVR for the remaining 26 sites in California.
Presenting Author: Alan Yong
Authors
Alan Yong yong@usgs.gov U.S. Geological Survey, Pasadena, California, United States Presenting Author
Corresponding Author
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Fumiaki Nagashima nagashima@sere.dpri.kyoto-u.ac.jp University of Kyoto, Uji, , Japan |
Eri Ito ito@sere.dpri.kyoto-u.ac.jp Disaster Prevention and Research Institute, University of Kyoto, Uji, , Japan |
Hiroshi Kawase kawase@sere.dpri.kyoto-u.ac.jp University of Kyoto, Uji, , Japan |
Jon B Fletcher jfletcher@usgs.gov U.S. Geological Survey, Menlo Park, California, United States |
Koichi Hayashi khayashi@geometrics.com Geometrics, San Jose, California, United States |
Antony Martin amartin@geovision.com GEOVision Incorporated, Corona, California, United States |
Alex Grant agrant@usgs.gov U.S. Geological Survey, Moffett Field, California, United States |
Devin McPhillips dmcphillips@usgs.gov U.S. Geological Survey, Pasadena, California, United States |
Comparison of Vs30 and F0 Values by the Single Station Earthquake-to-Microtremor Ratio (EMR) Method to Those by Traditional Multi-Station Array-Based Site Characterization Methods
Category
Data Fusion and Uncertainty Quantification in Near-Surface Site Characterization